1. Field of the Invention
The present invention relates to a continuous reinforcing fiber sheet which is well applicable as an intermediate base material or a structural member for an FRP-formed product, or as a reinforcing member for a metal tube post or a plastic pipe used for an illuminating pole, a sign pole or an electric pole, or as a reinforcing member for a civil engineering or building structure and which permits the improvement of torsional rigidity, and a manufacturing method of the continuous reinforcing fiber sheet.
2. Description of the Related Art
When producing a wing or a fuselage of an airplane, a blade of a windmill, or a large-scale structure such as a ship or an automobile, it is the recent practice to use, for example, I-shaped, H-shaped, T-shaped, L-shaped, rod or shaft-shaped, or pipe or tube-shaped continuous long fiber reinforced plastic structural members.
Such a long fiber reinforced plastic structural member can be produced by the so-called pultrusion process which comprises impregnating a unidirectional reinforcing fiber sheet having reinforcing fibers arranged along the main axis direction with a matrix resin, and continuously feeding the resultant impregnated sheet to a mold for forming the sheet.
The long fiber reinforced plastics can be formed also by preparing a prepreg by impregnating the reinforcing fiber sheet with a hot-melt epoxy resin, and continuously heating and pressing a plurality of such prepregs in lamination into a prescribed shape.
However, the thus formed fiber reinforced plastic structural member, which permits the achievement of desired bending strength and rigidity, has a problem of a poor torsional rigidity because it is a formed product of unidirectional fibers.
It is therefore the conventional practice to affix the reinforcing fiber sheet prepared by arranging the reinforcing fibers in, for example, a 45xc2x0-direction onto a fiber reinforced plastic structural member.
The continuous reinforcing fiber sheet comprising the reinforcing fibers arranged in, for example, a 45xc2x0-direction to the main axis is not however existent at present, and it has been impossible to prepare a continuous molded product having an increased torsional rigidity by a forming method such as the pultrusion process.
There is available also a method of winding the reinforcing fibers around the fiber reinforced plastic structural member by means of an overwinder. It is however impossible to prepare an I-shaped or H-shaped fiber reinforced plastic structural member.
The torsional rigidity may also be improved by using a chopped strand mat of carbon fibers or glass fibers upon the pultrusion. However, the resultant product is seriously poor in the modulus of elasticity as compared with the case where the reinforcing fiber sheet comprising the reinforcing fibers arranged in a 45xc2x0-direction is used. A sufficient torsional rigidity cannot therefor be obtained.
It is not impossible, as shown in FIG. 11, to join together a plurality of reinforcing fiber sheets 102 prepared by cutting a reinforcing fiber sheet 100 made by arranging reinforcing fibers 101 in one direction so that the reinforcing fibers 101 are oriented at a prescribed angle such as 45xc2x0, and to use the resultant product in the pultrusion process.
In this case, however, the joining of the plurality of reinforcing fiber sheets 102 causes the overlapping of the joints of the reinforcing fiber sheets or produces the steps thereof. The thus formed fiber reinforced plastic structural member cannot therefore obtain a sufficient satisfaction in quality.
As a result of extensive studies and experiments, the present inventors obtained the following findings, as described later in detail. By arranging the reinforcing fibers of a prescribed length at a prescribed angle such as 45xc2x0 to the main axis on a continuous mesh-shaped support sheet, and adhering and holding them with the mesh-shaped support sheet, it is possible to suitably prepare the continuous reinforcing fiber sheet in which the reinforcing fibers are arranged at an angle of 45xc2x0; the continuous reinforcing fiber sheet having such a configuration is well applicable for the pultrusion process without the risk of the reinforcing fibers being dispersed into pieces; and it is possible to prepare the long fiber reinforced plastic structural member having a remarkably improved torsional rigidity.
In the continuous reinforcing fiber sheet having the configuration described above, the reinforcing fibers can be fixed in one direction at laps when winding it around a tubular product such as a pipe, thus permitting the remarkable improvement of the torsional rigidity.
The continuous reinforcing fiber sheet of the aforementioned configuration can serve as the continuous reinforcing fiber sheet having the reinforcing fibers oriented in a counter direction by reversing. It is therefore easy to laminate a plurality of layers symmetrically (symmetric lamination), whereby the conventional problem of bending upon the heating and forming of the sheet can be completely solved.
The present invention was developed on the basis of these new findings obtained by the present inventors.
It is therefore an object of the present invention to provide a continuous reinforcing fiber sheet, having reinforcing fibers arranged at an arbitrary angle to the main axis, which permits the use for pultrusion without the risk of the reinforcing fibers of being dispersed, and the preparation of a long fiber reinforced plastic structural member having a remarkably improved torsional rigidity, and a manufacturing method thereof.
Another object of the invention is to provide a continuous reinforcing fiber sheet which, when winding the same around an object of reinforcement such as a pipe for reinforcement, permits satisfactory fixing at lap portions in the circumferential direction, and improvement of torsional rigidity of the object of reinforcement, and a manufacturing method thereof.
Still another object of the invention is to provide a continuous reinforcing fiber sheet which permits the easy symmetric lamination of a plurality of layers of such fiber sheet (symmetric lamination), and completely resolves the problem of the bending occurred during the heating and forming thereof, and a manufacturing method thereof
The aforementioned objects of the invention can be achieved by the continuous reinforcing fiber sheet and the manufacturing method thereof of the invention. In summary, according to a first aspect of the invention, there is provided a continuous reinforcing fiber sheet which has not yet been impregnated with a resin, in the form of a continuous sheet shape. The continuous reinforcing fiber sheet comprises at least one continuous resin-penetrable support sheet, and a reinforcing fiber layer held by the resin-penetrable support sheet. The reinforcing fiber layer comprises reinforcing fibers which are long fibers having substantially a certain length arranged at a prescribed angle to the longitudinal direction of the resin-penetrable support sheet, and along the longitudinal direction of the resin-penetrable support sheet. The continuous reinforcing fiber sheet of the invention has a width within a range of from 10 to 150 cm and a longitudinal length of at least 10 m. According to an embodiment of the invention, the reinforcing fibers are arranged substantially at 45xc2x0 to the longitudinal direction of the resin-penetrable support sheet. According to still another embodiment of the invention, for the aseismatic reinforcement of a reinforced concrete column for civil engineering or building purposes, the continuous reinforcing fiber sheet can be adhered to the column with the reinforcing fibers substantially at an angle of 45xc2x0 to the longitudinal direction of the concrete column.
According to a second aspect of the invention, there is provided a multi-layer-shaped continuous reinforcing fiber sheet comprising two or more continuous reinforcing fiber sheets laminated into an integral sheet. According to an embodiment of this aspect of the invention, at least one such resin-penetrable support sheet is interposed between the laminated continuous reinforcing sheets. According to another embodiment of the invention, the reinforcing fibers forming a reinforcing fiber layer of each of the continuous reinforcing fiber sheets are arranged in a direction relative to the longitudinal direction of the resin-penetrable support sheets and at an angle, or, the reinforcing fibers forming the reinforcing fiber layer of each of the continuous reinforcing fiber sheets are oriented in a direction different from the longitudinal direction of the resin-penetrable support sheet.
According to a third aspect of the invention, there is provided a continuous reinforcing fiber sheet prepreg, wherein the continuous reinforcing fiber sheet is impregnated with a resin.
According to a fourth aspect of the invention, there is provided a manufacturing method of a continuous reinforcing fiber sheet in the form of a continuous sheet shape, which has not yet been impregnated with a resin, comprising the steps of:
(a) continuously supplying at least one resin-penetrable support sheet;
(b) supplying reinforcing fibers which are long fibers having substantially a certain length at a prescribed angle to the longitudinal direction of the resin-penetrable support sheet; and
(c) heating and pressing the resin-penetrable support sheet and a reinforcing fiber layer formed with the reinforcing fibers and laminated with the resin-penetrable support sheet. According to an embodiment of this aspect of the invention, the above mentioned step (b) is accomplished by winding the reinforcing fiber sheet formed by arranging the reinforcing fibers in a direction spirally around the resin-penetrable support sheets supplied continuously. The resin-penetrable support sheets are arranged on both sides of a sheet of release paper. The reinforcing fiber sheet heated, pressed and spirally wound around the resin-penetrable support. sheets arranged on both sides of the release paper is cut at both edge positions in the longitudinal direction of the sheet, making into two sheets.
According to an embodiment of the aforementioned aspects of the invention, the continuous resin-penetrable support sheet can be provided on a side or on both sides of the reinforcing fiber layer. According to another embodiment, the resin-penetrable support sheets are a mesh-shaped sheet or cloth. According to still another embodiment, the mesh-shaped sheet is a biaxial mesh-shaped sheet formed by warps in the same direction as the longitudinal direction of the continuous reinforcing fiber sheet and wefts at right angles to the warps.
According to another embodiment of this aspect of the invention, the reinforcing fibers forming the reinforcing fiber layer are selected from the group consisting of PAN-based or pitch-based carbon fibers, glass fibers, organic fibers such as aramide, PBO (polyparaphenylenebenzbisoxazole), polyamide, polyarylate, and polyester, and steel fibers, used singly or in mixture of a plurality thereof. The reinforcing fiber layer may have a unit weight within a range of from 100 to 600 g/m2.